Cali-Style Fried Egg Sandwich

For this healthy, creamy, and colorful sandwich, start with ripe avocado. A California favorite, an avocado is ready to eat just after the skin turns from green to black, and it yields to gentle pressure. Take the butter out of the refrigerator before you slice the red onion and tomatoes so it has time to soften. And choose a hearty, crusty Italian bread.